In conventional photography and in diffusion transfer photographic elements, it is known to provide a temporary barrier between layers through which processing solutions penetrate. A neutralization layer for stopping development and stabilizing images may be provided in photographic materials suitable for diffusion transfer processes in particular. It is well known that a temporary barrier layer may function as a timing mechanism (timing layer), for example, between the neutralization layer and a silver halide emulsion layer to prevent maximum density from being lowered by too rapid a neutralization of the developing solutions in the neutralization layer. This enables processing at a high pH to be continued for a predetermined period of time, before the neutralization of developing solutions (alkaline processing compositions) is initiated in the neutralization layer.
Generally, the development reaction of silver halide photography proceeds slowly at a low temperature, while the reaction proceeds rapidly at a high temperature. Accordingly, when a diffusion transfer process is utilized for instant photography, development is carried out not at a controlled temperature as in general photography, but at various temperatures. As a result, it is very important that photographic elements be capable of controlling the neutralization reaction of a developing solution according to the temperature so as to, (1) expedite the neutralization reaction of the developing solution at high temperatures at which the development reaction proceeds rapidly, and (2) allow the neutralization reaction of the developing solution to proceed slowly at low temperatures at which the development reaction proceeds slowly to obtain a good image even when the development temperature is changed.
In another embodiment, the temporary barrier layer is used as an interlayer for controlling the development of the silver halide emulsion of each light-sensitive layer. It is desirable that the barrier layer does not interfere with the diffusion of dyes after that layer has functioned as a short-time barrier to permit only the development of a particular layer.
When there is a mordant layer on a support on which silver halide emulsion layers are provided, it is desirable that the interlayer is a layer which does not function as a barrier to the penetration of water during coating and storage, so that the silver halide emulsion layers are not affected by the mordant layer, for example, during storage.
Further, it is known that in photographic elements for use in diffusion transfer processes wherein alkaline processing compositions are spread between two sheets, the sheets are provided with a temporary barrier layer to the alkaline processing compositions so that the development of the silver halide emulsions is not retarded or the alkaline processing compositions are not excessively spread as a result of the alkaline processing solutions being prematurely absorbed by the sheets.
Examples of materials used as a temporary barrier layer for the above-described purposes include the aqueous latex type polymer materials described in JP-A-53-72622 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-54-138432, JP-A-54-138433, JP-A-55-70839, U.S. Pat. Nos. 4,250,243 and 4,199,362. Examples of the materials used as timing layers which can be coated by organic solvents include the organic solvent-coatable latex type polymer materials described in JP-A-56-25735 and JP-A-56-97346, .beta.-elimation type polymer materials described in JP-A-55-121438, U.S. Pat. Nos. 4,288,523, 4,426,481, 4,391,895 and 4,297,431, JP-A-59-136732 and JP-A-59-212836, ring opening type polymer materials having a lactone ring on a side chain described in JP-A-57-141634 and ring opening type polymer materials having a lactone ring in its main chain described in JP-A-55-54312 and JP-A-58-125037. Further, U.S. Pat. Nos. 4,061,496 and 4,357,392 disclose timing layers composed of two layers consisting of a layer comprising an aqueous latex type polymer material and a polymer layer coated with an organic solvent.
Further, JP-A-55-41490 discloses graft copolymers. However, the reaction system which generates a radical in the backbone chain must be an aqueous system from the viewpoint of easy synthesis. Accordingly, the polymers to be used are limited to those whose backbone chain is highly water-soluble or water-swellable. Furthermore, JP-A-49-22935 discloses temporary barrier layers composed of a combination of a developing solution-impermeable matrix (e.g., a butyl acrylate layer) comprising an aqueous film-forming synthetic polymer dispersion and a dispersion phase comprising a developing solution-penetrable material (e.g., polyacrylamide). However, there are the disadvantages that the combination is limited to an aqueous system/aqueous system, and the combinations capable of forming a uniform film are a little.
However, there is often the problem that when these compounds are coated on multi-layer photographic materials, the coated films are brittle and can not withstand repeated bending. Further, this problem is often so serious that the coated films are cracked or peeled off because of the bending after development. Furthermore, there is the problem that such temporary barrier layers comprising a two layer structure cause an increase in production costs even without the problem of brittleness.